The invention relates to a support structure for a pipe and to a method for providing such a support structure for a pipe. The method in particular relates to a support structure and method which offers a reduced tendency to produce mechanical damage at the point of contact between the support and the pipe and/or a reduced tendency to create a corrosion site at the point of contact between the support and the pipe.
The invention in particular relates to a support structure for a pipe to form part of an industrial pipeline system such as might be required for the transport of fluids in, around and between large scale industrial facilities such as chemical and petrochemical plants, power generation facilities and the like.
The invention in particular relates to a support structure and method for the support of pipelines fabricated from pipeline steel and other similarly potentially corrodible materials.
Various industrial applications exist where it becomes necessary to construct a network of pipelines for the long distance transport of liquids and gases at ambient or elevated temperatures, for example in conjunction with various industrial applications. A typical pipeline construction consists for instance of a plurality of pipes connected end to end, of suitable structural material and for example structural steel. These may be retained stably in position, and for example supported on the ground or another surface, by provision of a plurality of support plates with a first face in contact with and supporting a pipe and a second opposing face held by a suitable support structure, such as support leg engaging the ground or another surface along which the pipeline is run. The pipe is supported for example by being seated in face-to-face contact with a first face of the support plate and; or by being clamped thereon. Such support plates are generally known, and might for example have an arcuate configuration sized and shaped for face-to-face contact with a corresponding shaped lower surface of a cylindrical pipe.
Pipelines to which the prior art structures and the structures of the invention relate are typically envisaged to be exposed to mild to moderate corrosive conditions, for example by being in an external ambient environment and subject to adverse weather conditions, and possibly in the case of application in coastal areas or offshore subject to the corrosive effects of seawater. Galvanic reaction between dissimilar metals making up the pipeline and support plate may also have a detrimental role.
To mitigate this, pipes fabricated from steel or the like are typically provided with anti-corrosion coatings, anti-corrosion paints or the like applied to an external surface.
Even so, two problems in particular can arise with simple prior art supports in which a lower part of the pipe is supported, and for example clamped, at a contact region on an upper surface of a support plate.
First, potentially corrosive materials from the external environment, such as water and saline solution and the like, tend to accumulate in the contact region where the lower surface of the pipe and the upper surface of the support lie adjacent to one another. Thus, this region becomes a particular site for likely corrosion over time as a result of environmental effects.
Second, physical and mechanical contact between the support and the contacted surface on the pipe can damage by mechanical action over time any anti-corrosion paint or other coating applied to the external surfaces of the pipes in the contact region. In particular, stresses and strains tending to cause relative movement of the respective surfaces, for example by differential expansion or contraction due to changes of ambient or carried fluid temperature, physical movement of the pipeline as a result of internal or external forces etc, can produce sliding between the pipe surface and the support at the point of contact, exacerbating any mechanical damage which might be caused to an anti-corrosion coating on the pipe surface.
These effects combine to tend to produce a particularly corrosion-susceptible site in the region of contact between the support and the lower surface of the pipe seated/clamped thereon.
GB2175667A describes a support structure for a pipe having a number of the above characteristics, which purports to mitigate some of the indicated problems. A support structure includes a convex plate made of corrosion-resistant material fitted to and in contact with a lower part of the outer surface of a pipe with the interposition of a layer of anti-corrosive adhesive material which adheres the support plate to the pipe.
The use of a bonding agent to adhere the support plate to the pipe in this manner is not considered to be desirable on thermal and/or ambient pipework for a number of reasons.
Amongst the problems that can arise in such a system are that:
the bonding agent may be affected by heat causing the bond to tend to act as a lubricant allowing for slippage;
the bonding agent may become brittle over time and tend to delaminate from the steel surfaces;
the bonding agent requires direct bonding to the steel pipe, so additional protection cannot be provided, and the result is that the steel of the pipe surface is exposed if the bond fails;
if the bond does fail this may result in a capillary action between the pipe and the bond exacerbating the corrosion problem by creating a pocket trap effect;
the solution is unsatisfactory because it requires the pipe to be directly modified in situ.